Recently, nanoparticle (NP) superstructures have become an important pathway to the creation of smart materials with new functionalities. Most of the current examples of complex NP systems, such as bioconjugates or hybrid nanocolloids and their lattices, are typically static, i.e. have limited response to the environmental parameters and do not exhibit smooth reversible transitions of their 3D organization/geometry in response to external stimuli. Dynamic NP superstructures with gradual structural adaptation to common physical parameters may reveal interesting analogies with biological entities similar in scale. Additionally, such systems can also find technological applications as novel optical devices.
A need exists for new sensor materials with physical dimensions as to require no substrate. This feature will make possible the sensor's utilization in nanofluidic devices and in other strongly confined spaces, where other sensors can not reach. Developing NP assemblies that are soluble in water, one can experimentally measure the 3D property distributions, which may include concentration, temperature, and pH gradients. These data are of critical importance for understanding both chemical and physical processes in confined fluids. Careful design of the superstructure addressing biocompatibility can also produce sensors of monitoring of biological reactions in the confinements of a single cell.
New sensors should have photostability greater than that of organic dyes, which have been used in the luminescent tags, but it is equally important for the long-term observation of biological objects. The processes used by the sensors should be reversible. The sensors should provide high sensitivity and high signal/noise. The sensors should have a wide range of biological selectivity.